1. Field of Invention
This invention generally relates to the field of the treatment of occlusive disease and in particular, to an improved surgical method for treating occlusive disease.
2. Prior Art
Percutaneous coronary intervention and percutaneous transluminal angioplasty are medical procedures used to widen occluded blood vessels. These procedures are often accompanied by insertion of a stent to help keep the occluded vessel open. However, current stents, while sufficient in mechanical strength and durability to keep occluded vessels open, fail in that they cause inflammation and immune responses that encourage re-blocking of the blood vessel in a condition known as restenosis. In addition to the problems of inflammation and restenosis, retrieval of an implanted stent (usually because of restenosis, and sometimes because of severe inflammatory or immune responses) involves difficult and risky surgical procedures. Generally, all current stents must be retrieved and replaced sooner or later due to restenosis (the exact rate of restenosis varies in different people), usually within 10 years. People with severe inflammatory or immune responses often need to have their stent removed within a few months or a year. Surgeons need to perform open heart surgery to retrieve an implanted stent. There are numerous health-related issues, risks, and concerns, including death, that accompany open heart surgery.
Biliary stent implantation is a medical procedure used to treat problems associated with blockages in the bile ducts. The procedure involves the implantation of a stent to help keep the occluded passageway open. Current stents used in the bile ducts can cause inflammation and immune responses and also are not easily retrievable, sometimes requiring surgery. Biliary stents often need to be replaced every few months (because they get clogged up); thus, the fact that current stents are not easily retrievable is a major problem as they may need to be replaced frequently.
Stents are also implanted in other structures to treat occlusions. These structures include, but are not limited to, the peripheral arteries and veins, esophagus, trachea or large bronchi, ureters, and urethra. Current stents used in these structures can cause inflammation and immune responses and often are not easily retrievable, sometimes requiring surgery. Stents in some of these structures may also need to be replaced relatively frequently, something that presents a major problem associated with current stents since current stents are not easily retrievable once placed.
The prior art consists of surgical methods involving stents in the two existing categories: metallic wire mesh, and bioresorbable. Both such categories have flaws. The metallic wire mesh stents cause inflammatory and immune responses that may lead to restenosis, besides causing other localized tissue damage and trauma. The bioresorbable stents' only advantage over metallic wire mesh stents is that they degrade and go away after 5 to 10 years. Otherwise, they behave exactly the same as wire mesh stents: a similar, if not increased, rate of immune responses (especially due to breakdown/degradation products generated during stent degradation), a requirement for surgical intervention if removal becomes necessary, and a similar, if not increased, rate of inflammatory responses (especially due to breakdown/degradation products generated during stent degradation).
Bioresorbable stents were invented to deal with the core problem of metal stents: inflammatory and immune responses eventually lead to restenosis, blocking the duct or vessel the stent originally opened, and requiring retrieval of the stent, which often involves highly invasive surgical procedures. Bioresorbable stents attempted to solve this problem by degrading in vivo within five to ten years; however, serious immune and inflammatory responses caused by this degradation often occur before the stent is completely degraded, in which case the stent must be surgically removed. Also, the associated memory immune responses associated with the immune responses and inflammation often preclude bioresorbable stents from being used more than once in a person (that is, it is often not medically sound to implant a second bioresorbable stent in a person after the first bioresorbable stent has degraded or been retrieved).
The surgical method of the present invention involves a one-piece retractable stent that belongs to a completely different stent category and is the first and only member of this new category. It is made of a one-piece sheet material (such as an elastic metallic polymer). Also, it is not bioresorbable. Because it is one-piece (which minimizes damage to the luminal membranes of ducts or vessels the stent is deployed in), and because it is not bioresorbable, it prevents, or at least minimizes, inflammation, immune responses, and restenosis. Unlike the stents in both existing categories of stents, the structure of the invention allows it to be collapsed when desired at any time and then retrieved easily, without need for highly invasive surgical intervention (e.g., if deployed in a coronary artery, open heart surgery would not be necessary to retrieve my stent). Existing stents cannot be collapsed due to their design; once expanded/deployed, their many pieces lock into place permanently, making it impossible to collapse the stent, and thus making it impossible to retrieve the stent without complicated surgical procedures (such as open heart surgery in the case of coronary stents).
As such, there is no relevant prior art pertaining to the method for surgical treatment of occlusive disease of the invention.
3. Objects and Advantages
Current surgical methods involve stents that fall into two broad categories: metallic and bioresorbable. Both metallic and bioresorbable stents are non-retractable and are made up of many interconnected parts, similarly to a metal wire fence. The stent involved in the surgical method of the invention is in a new third category: one-piece (sheet) retractable stent. It consists of a much simpler one-piece design rather than a wire mesh and is simply made of a material (e.g., an elastic metallic polymer) fabricated into a continuous non-porous sheath. Thus, there is no prior art relevant to the invention.
The surgical method of the invention provides much needed improvements over existing surgical methods involving metallic or bioresorbable stents. The method of the invention provides a stent with the novel feature of retractability, a stent that thus never requires open heart surgery for removal. Also, the stent provides reduced inflammation and immune responses over both metallic and bioresorbable stents.
To summarize, several objects and advantages of the present invention are:
(a) to allow retractability of an implanted stent, solving an important problem associated with implanted metal or bioresorbable stents. The stent involved in the invention functions similarly to a regular metal stent, but, because of its special one-piece sheet design, can be retracted with a special retractor in a minor surgical procedure similar to the procedure for implanting the stent (without major surgery, such as open heart surgery in the case of coronary stents) and replaced with a new stent if and when it needs to be replaced with a new one;
(b) to allow the use of a simple, inexpensive, and easily constructed stent that can be manufactured in several standard lengths and diameters, but can also be made to special non-standard specifications easily and cheaply, upon order;
(c) to allow the use of a smooth one-piece stent that naturally (due to its smooth one-piece nature) inhibits the biological mechanisms leading to restenosis, leading to a longer functional operating time per stent.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.